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. 2018 Nov 20;8:17101. doi: 10.1038/s41598-018-35513-1

Figure 2.

Figure 2

XRD patterns of the as-prepared UCNP: (a) 180 °C, (b) 190 °C, (c) 200 °C, (d) 210 °C. Particles corresponding to both α-NaYF4, PDF 00-027-0688 and β-NaYF4, PDF 00-016-0334 are observed. (e) Schematic illustration of the phase transformation of the UCNP with increasing HR time.